1. Field of the Invention
The present invention relates to a thin-film transistor and a display device which is operated using the thin-film transistor.
2. Description of the Related Art
As a kind of field-effect transistor, a thin-film transistor in which a channel region is formed in a semiconductor layer formed over a substrate having an insulating surface is known. Techniques in which amorphous silicon, microcrystalline silicon, or polycrystalline silicon is used for the semiconductor layer used in the thin-film transistor have been disclosed (see Patent Documents 1 to 5). A typical application of a thin-film transistor is a liquid crystal television in which the thin-film transistor has been put to the practical use as a switching transistor for each pixel included in a display panel.    [Patent Document 1] Japanese Published Patent Application No. 2001-053283    [Patent Document 2] Japanese Published Patent Application No. Hei05-129608    [Patent Document 3] Japanese Published Patent Application No. 2005-049832    [Patent Document 4] Japanese Published Patent Application No. Hei07-131030    [Patent Document 5] Japanese Published Patent Application No. 2005-191546